1. Field of the Invention
The invention relates to a method of and apparatus for correcting a sequence of samples which are considered as invalid, of an equidistantly sampled signal, on the basis of replacement values derived from sequences of valid samples.
2. Description of the Related Art
Such a method and apparatus are described in applicant's copending U.S. application Ser. No. 898,460 (PHN 11,716) filed concurrently herewith, which claims priority based on a Netherlands patent application. Such U.S. application also references a pending application, assigned to the present assignee, filed Mar. 30, 1988 as a continuation of U.S. application Ser. No. 601,817, filed Apr. 19, 1984, now abandoned, disclosing a different kind of restoration technique for invalid signal samples.
The restoration technique described in such concurrently filed U.S. application requires the availability, immediately after a sequence of samples to be restored, of a relatively long subsequent sequence of valid samples. More specifically, the length of such a subsequent sequence must correspond to a maximum anticipated instantaneous periodicity of a signal segment of which the sequence of samples to be restored forms part. For example, for speech sampled at a rate of 8000 Hz such a subsequent sequence must comprise approximately 160 samples. Consequently, a delay of 20 msec is introduced after the appearance of the sequence of samples to be restored before the result of the restoration procedure can be made available.
In addition, the implementation of the above-described restoration technique requires that the periodicity of a signal segment containing the sequence of samples to be restored must be estimated. The replacement values for restoring invalid samples are then determined by solving a system of equations in which the replacement values are unknown factors.